Retail fuel dispensers and pumps are used to fuel automobiles. Service stations have underground storage tanks which contain the fuel to be delivered. Basic fuel dispensers or pumps are comprised of a housing, internal delivery chambers, meters, control electronics and devices, hoses and nozzles for delivery of fuel, and display units to show the amount of fuel dispensed. The pumping unit to drive the fuel through a dispenser and out through the hose and nozzle is contained in the underground storage tank. Dispensers are the most common type of retail fuel delivery device used in the United States. Pumps also contain all of the basic elements of a dispenser, but the pumping unit is found inside the pump housing itself rather than in the underground storage tank. For the purposes of this application, the terms "dispenser" and "pump" are used interchangeably.
One core responsibility of a dispenser is to measure the amount of fuel delivered to the customer. This measurement is performed by meters in the dispenser. Fuel comes from the underground storage tank into the dispenser through some type of conduit or chamber controlled by a valve which can open and close to allow and preclude the flow of fuel. After the fuel passes through the valve, the fuel flows through a metering device. There are many types of metering devices, but the most common type of meter used in dispensers is a positive-displacement meter. A positive displacement meter measures the amount of fluid by counting the number of displacements of a known volume. For every such displacement, a quantifiable number of electronic pulses is generated by an electromechanical pulser connected to the meter. Therefore by knowing the number of pulses, the volume of fuel flowing through the meter is ascertainable by the dispenser. Basic dispensers as the one described here only allow the ability to deliver a single octane or grade of fuel to a customer.
A recent development in dispenser technology is the ability of a single dispenser to deliver multiple octane levels of fuel to a customer. One of this type of dispenser is sold under the brand MPD.RTM. which is a registered trademark of Gilbarco Inc. A MPD.RTM. dispenser usually contains one meter for every grade of fuel available to the customer. Different octanes or grades of fuel are stored separately in underground storage tanks. The dispenser delivers fuel from the correct underground storage tank depending on the grade of fuel selected by the customer. For example, if the customer selects octane grade 89, the dispenser will draw fuel from the underground storage tank containing that product, measure the fuel through a meter for measurement and route the fuel to the appropriate hose and nozzle for delivery to the customer.
A more recent evolution of technology in dispensers involves blending systems. Blending dispensers, called blenders, are used to dispense a plurality of different octane grades of fuel by blending a high octane and a low octane fuel to create one or more mid-level octane fuels. Blenders are advantageous, because service stations can deliver multiple grades of fuel without having to provide a separate underground storage tanks for each grade of fuel. Service stations using blending dispensers need have only two underground storage tanks, one for the high octane fuel and the other for the low octane fuel. Also, blenders require only two meters; one meter for the high octane and one meter for the low octane. For example, if a service station wants to install blenders capable of delivering 87, 89, 91, 92 and 93 octane fuels, the intermediate octane fuels of 89, 91, and 92 can be created by blending the correct proportions of 87 and 93 octane fuels. Additional information concerning blending dispensers is contained in Gilbarco Inc. brochure number P1876B titled "Blending With Gilbarco" the content of which is incorporated herein by reference. A patented example of a blending system is that described in U.S. Pat. No. 4,876,653 titled "Programmable Multiple Blender" ("the '653 patent") assigned to Gilbarco Inc. the content of which is incorporated herein by reference. The '653 patent discloses a system for blending low and high octane gasoline with the fuel flow rate in each of two fuel flow paths being under individual closed loop control. The system includes an algorithm for comparing the ratio of the actual accumulated volumes of the low octane to the high octane fuel relative to a statistically determined ratio of the ideal volume of the low to high octane fuel for the total accumulated volume of the sum of the volumes of the fuels at a given time. The system provides a very exact blend relative to a pre-selected blend ratio. In dispenser blending systems, it is imperative to have a meter for both the high and low octane fuels so that the dispenser can determine the amount of high and low octane fuel being blended to produce the correct ratio of blended fuel. For example, a dispenser may have 93 octane as it its high octane fuel and 87 as its low octane fuel. If the dispenser is setup to produce one intermediate grade of fuel at 90 octane, the dispenser must meter each grade independently and provide a control mechanism to control the high and low octane fuels at a 50/50 ratio. The actual octane level of the blended fuel is not measured in the dispenser.
An alternative blending system is disclosed in U.S. Pat. Nos. 5,038,971 and 5,125,533, the content of which is disclosed herein by reference.
Another further development in fuel dispensing systems is disclosed in U.S. Pat. No. 5,630,528 entitled "Method And Apparatus For Metering And Dispensing Fluid, Particularly Fuel" ("the '528 patent") assigned to Gilbarco Inc. The content of the '528 patent is incorporated herein by reference. This patent discloses a fuel dispenser which employs a single meter to measure multiple octane grades of fuel. It is more cost effective to have one single meter in a fuel dispenser than multiple meters. The system described in the '528 patent does not allow blending of fuels while still employing a single common meter. Heretofore blending dispensers have required two meters to measure both the high and low octane fuels to produce a desired ratio of each for intermediate fuel grades. For example, if the high octane grade is 93 and the low octane grade is 87, then a 50/50 blend ratio would produce an octane grade of 90. A blending dispenser known in the art today can determine only if a 50/50 ratio is being achieved by using two meters; one meter measures the amount of high octane fuel and the other meter measures the amount of low octane fuel. Because dispensers employing single meters are not manufactured by retail dispenser companies today, no one to the knowledge of the inventor has disclosed a solution to allow dispensers to employ a single meter, but also provide blending. Blending systems known in the art require at least two meters to produce a proper ratio of a blended fuel.
The advent of real time octane sensors provides a solution to the problem described above. The use of an octane sensor provides a method of blending totally different from the blending systems known in the dispenser art today. Because the octane sensor can measure the actual octane level of a blended fuel, two separate meters for both the low and high octane fuels are no longer necessary. An octane sensor can be included as a control parameter for octane blending in the control device of the dispenser. An example of such a sensor is that disclosed in Clarke et al., U.S. Pat. No. 5,225,679 the content of which is incorporated herein by reference. This sensor monitors hydrocarbon-based fuel properties using a mid-IR light source to illuminate fuel in a side stream flow provided for octane monitoring. The light passing through the fuel is received by a narrow bandwidth detector. The molecules of the fuel components are excited by the mid-IR light, and the amount of absorption exhibited by these excited molecules is detected and used to identify the presence of and to quantify the volume percent of the fuel components in solution. This information maybe used to determine known properties of the fuel solution to include octane levels.
A method of determining octane rating of fuel is also disclosed in U.S. Pat. No. 5,606,130 to Sinha et al. the content of which is incorporated herein by reference. The octane rating is determined by measuring the acoustic resonance in fuel and directly relating the resonance characteristics to experimentally observed values for known octane ratings.
The use of an octane sensor in a blending dispenser is a novel way to overcome the obstacle of requiring two separate meters to meter blending components.